400 Years of the Galilean Satellites

Posted By Emily Lakdawalla

2010/01/07 03:34 CST

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It was 400 years ago today that Galileo discovered smaller planets attending the planet Jupiter. Jason Perry is doing a far better job than I could of writing about the momentous discovery on his blog, the Gish Bar Times. This post serves as an index to his thoroughly researched history, and he's also maintaining an index to other bloggers' writings on the topic here.

In addition to Jason, I also want to highlight the ongoing work of Paul Schenk, who will soon be publishing an Atlas of the Galilean Satellites. He's been studying outer planet moons -- more specifically, the topography of outer planet moons (and what that says about their geology) -- since the 1980s. While in Padua for an event celebrating the anniversary, he uploaded a bunch of spectacular 3D flyovers of the Galilean moons to his Youtube channel; numerous screen grabs from his movies can be viewed at his blog, Dr. Schenk's 3D House of Satellites. My favorites include this one, showing a nine-kilometer-high mountain peak next to a caldera on Io:

...and this one, showing the rumpled, peaky terrain of Callisto's plains.

oth are vertically exaggerated, the Callisto one much more than the Io one.

Paul Schenk

Agenor Linea, Europa

Stretching 1400 kilometers across Europa, Agenor Linea is a mysterious feature composed of numerous parallel ridges. In this view, made from Galileo data, we see a part of Agenor that is 20 kilometers wide, with a few hundred meters of relief from ridge top to trough bottom (there is some vertical exaggeration). Adjacent to Agenor are regions of chaos. Mapping suggests that some strike-slip motion has occurred across the feature. Click to view a video flying over this feature.